Method of manufacture of nuclear radiation sources

ABSTRACT

A method of manufacturing a radioactive source comprising applying a radioactive material onto a substrate, then heating the radioactive material and the substrate to form a radioactive layer applied to the substrate. In order to apply a metal oxide sealing layer onto the radioactive layer, the radioactive layer is heated and a film of a chloride of titanium, tin, zirconium, aluminum or chromium is applied onto the heated radioactive layer and the chloride metal film is hydrolyzed to form the oxide sealing layer.

United States Patent 1191 Drahkina et al.

[ 51 Oct. 29, 1974 METHOD OF MANUFACTURE OF NUCLEAR RADIATION SOURCES[22] Filed: Feb. 15, 1972 Appl. No.: 226,541

Related U.S. Application Data 765,274, Oct. 2, 1968,

Division of Ser. abandoned.

[52] U.S. Cl 117/220, 11 7/69, ll 7/ 1 06 A, 117/106 R, 176/82 51] 111;,(31..., r g 2'0 W [58] Field 01 Search..... 117/107.2 R, 106 A, 106 R,

[56] References Cited UNITED STATES PATENTS 2,894,846 7/1959 Stoddard117/220 X 3,122,595 2/1964 Oxley ll7/l07.2 R X Primary Examiner-RalphHusack Attorney, Agent, or Firm-Eric H. Waters [5 7] ABSTRACT A methodof manufacturing a radioactive source comprising applying a radioactivematerial onto a substrate, then heating the radioactive material and thesubstrate to form a radioactive layer applied to the substrate. In orderto apply a metal oxide sealing layer onto the radioactive layer, theradioactive layer is heated and a film of a chloride of titanium, tin,zirconium, aluminum or chromium is applied onto the heated radioactivelayer and the chloride metal film is hydrolyzed to form the oxidesealing layer.

5 Claims, 1 Drawing Figure METHOD OF MANUFACTURE OF NUCLEAR RADIATIONSOURCES CROSS-RELATED APPLICATION This Application is a division ofcopending Application Ser. No. 765,274 filed Oct. 2, 1968 and nowabandoned.

The present invention relates to methods of manufacture of nuclearradiation equipment and more specifically, to radioactive sources forremoving electrostatic charges and for calibrating measuringinstruments.

Existing radioactive sources are fabricated by applying a sealing layerin the form of a fused enamel on a radioactive layer applied onto anenameled metallic substrate.

The manufacture of radioactive sources by the above-mentioned method islaborious, complicated and a slow operation, while the sources sufferfrom lack of hermeticity, resulting in contamination of thesurroundings. Also, in such sources much of the radiation is absorbed bythe fairly thick layer of fused enamel.

It is an object of this invention to provide a method of manufacturing aradioactive source in which no diffusion of the radioactive material tothe surface of the source occurs.

It is another object of this invention to provide method in which amechanically strong radioactive source is produced.

Still another object of this invention is to provide a method forproducing a radioactive source in which the loss of nuclear radiation inthe sealing layer is minimized to -18 per cent.

It is also an object of this invention to provide a simple andproductive method for manufacturing said radioactive sources, which doesnot use critical materials.

With the above and other objects in view, a radioactive source isproduced comprising a sealing layer which is a film of oxides oftitanium, tin, zirconium, aluminum and chromium, used either separatelyor in combination.

In the manufacture of radioactive sources, this film of metal oxides isproduced by hydrolysis of the chlorides of these metals on a heatedradioactive layer applied onto a substrate.

The foregoing makes it possible to manufacture inexpensive, high-qualityradioactive sources which may be widely used for removel ofelectrostatic charges in various industries.

Other objects and advantages of the invention will become more fullyapparent from the following description of a specific embodiment whenread in connection with the accompanying drawing the sole FIG- URE ofwhich shows a cross-sectional view of the source of the presentinvention.

A radioactive source, according to the invention, comprises a substrate1 coated by a layer of priming silicate enamel 2. From one side thepriming enamel 2 is overlaid by a coat of finish enamel 3 on to which isapplied the radioactive material 4, the said material being an alloy offinish enamel 3 and a radioactive substance. The radioactive material 4is coated by a sealing layer 5 which is a film of a metallic oxide, suchas titanium dioxide. As an alternative, the layer 5 may be obtained fromoxides of tin, zirconium, aluminum and chromium, used either separatelyor in combination.

The substrate 1 of the radioactive source may be a glazed ceramicmaterial, and also steel onto which the radioactive material is directlyapplied.

The method of manufacturing the herein proposed radioactive sourceconsists in the following.

The radioactive material is applied to the finish coat of enamel 3 onthe already enameled substrate 1. The radioactive material may beapplied as a solution of a definite acidity, or as an oxide (mixed withenamel) by electrophoresis. The choice of the method for the applicationof the radioactive material is determined by the weight of one curie ofthe radioisotope used.

The application of the radioactive material as a solution is well known.

In the application of the radioactive material by electrophoresis, thesubstrate 1 is preliminarily given a coat of a metal readily soluble inmolten enamel. The radioactive material as an oxide, along with theenamel to be applied together with it, is finely comminuted.Electrophoresis is carried out for 0.5 to 2 minutes. The design of theelectrophoresis apparatus depends on the configuration of the sourcebeing made. The applied radioactive material, after the liquid phase hasbeen driven off by drying, is fused with the finish enamel 3 at atemperature of 800 to 900C, with the formation of a radioactive layer 4which has a smooth, bright surface, free from defects such as pin-holes,burned spots, blisters, and the like. On cooling, the source is washedin running water to remove the loose radioactive material.

The source is sealed off with the metal oxides, such as titaniumdioxide, by producing a film of a metal oxide on the radioactive layer 4heated to a temperature of 200 to 650C, by means of vapor-phasehydrolysis of the chloride of a given metal, such as titaniumtetrachloride. The sealing operation is continued until a sealing layeris produced in the form of a film of titanium dioxide, or of any othermetal used.

If the sealing layer is to be current-conducting, the layer can beobtained by hydrolysis of tin tetrachloride with the formation of tindioxide in the form of a film.

A sealing layer in the form of a film of metallic oxide may be obtainedby liquid-phase hydrolysis of the respective metallic chlorides, andalso by pyrolysis of organometallic compounds.

The radioactive source manufactured by the present method, does notcontaminate the surroundings, is safe to handle, is strong mechanically,and is stable chemically and thermally.

While the invention has been described in connection with a preferredembodiment, it will be understood that various modifications andadaptations may be made without departing in any way from the spirit andscope of the invention, which will be readily comprehended by thoseskilled in the art.

Such modifications and adaptations should and are intended to becomprehended within the meaning and range of equivalence of the claimsthat follow.

What is claimed as new and desired to be secured by Letters Patent is:

l. A method of manufacturing a radioactive source, comprising applying aradioactive material onto a substrate; heating said radioactive materialand said substrate to form a radioactive layer applied to saidsubstrate; heating the radioactive layer applied to said substrate; andhydrolyzing a metal chloride by vapor phase active material is appliedonto the substrate by fusing said radioactive material with the enamelat a temperature of 80090()C.

5. A method as claimed in claim 1 wherein the radioactive material andsubstrate are heated to a temperature of 200-650C to enable thehydrolysis of the

1. A METHOD OF MANUFACTURING A RADIOACTIVE SOURCE, COMPRISIING APPLYIINGA RADIOACTIVE MATERIAL ONTO A SUBSTRATE; HEATING SAID RADIOACTIVEMATERIAL AND SAID SUBSTRATE TO FORM A RADIOACTIVE LAYER APPLIED TO SAIDSUBSTRATE; HEATING THE RATIOACTIVE LAYER APPLIED TO SAID SUBSTRATE; ANDHYDROLYZING A METAL CHLORIDE BY VAPOR PHASE HYDRROLYSIS TO FORM A METALOXIDE SEALING LAYER ON THE HEATED RADIOACTIVE LAYER.
 2. A method asclaimed in claim 1 wherein said substrate is coated with enamel prior toapplication of the radioactive material thereto.
 3. A method as claimedin claim 2 wherein said radioactive material is applied onto the enamelcoated substrate in combination with a finish enamel.
 4. A method asclaimed in claim 2 wherein said radioactive material is applied onto thesubstrate by fusing said radioactive material with the enamel at atemperature of 800*-900*C.
 5. A method as claimed in claim 1 wherein theradioactive material and substrate are heated to a temperature of200*-650*C to enable the hydrolysis of the metal chloride.